Datasheet

2
OUT
con OUT DS(on)
IN
V
P = I r
V
´ ´
2 9
sw IN OUT SW
P = V l 0.25 10 f
-
´ ´ ´ ´
9
GD IN SW
P = V 3 10 f
-
´ ´ ´
6
SUP IN
P = 116 10 V
-
´ ´
TOT CON SW GD SUP
P = P + P + P + P
J A JA TOT
T T Pq= - ´
A(max) J(max) JA TOT
T T Pq= - ´
TPS5401
www.ti.com SLVSAB0 –DECEMBER 2010
Power Dissipation Estimate
The following formulas show how to estimate the IC power dissipation under continuous-conduction mode (CCM)
operation. These equations should not be used if the device is working in discontinuous-conduction mode
(DCM).
The power dissipation of the IC includes conduction loss (P
con
), switching loss (P
sw
), gate-drive loss (P
GD
), and
supply current (P
SUP
).
(36)
(37)
(38)
(39)
So total power dissipation is:
(40)
For a given ambient temperature T
A
, the junction temperature T
J
can be estimated by Equation 41.
(41)
where:
• q
JA
is the thermal resistance of the package (°C/W)
For given T
J
(max) = 150°C, the maximum allowed ambient temperature can be estimated by Equation 42.
(42)
There are additional power losses in the regulator circuit due to the inductor ac and dc losses, the catch diode
and trace resistance that impact the overall efficiency of the regulator.
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